(1) Field of the Invention
This invention relates to a process for reacting phenol, mono- and di-alkyl phenols having at least one free o-position with methanol and/or dimethyl ether in the gas phase to form o-substituted phenols in the presence of a catalyst of oxides of iron, vanadium, at least one oxide of boron, aluminum, titanium, zirconium, silicon, germanium, tin and lead, and at least one oxide of an alkali metal, alkaline-earth metal, lanthanum and manganese.
(2) Description of the Prior Art
The production of o-substituted phenols, for example o-cresol and 2,6-dimethyl phenol is of considerable commercial interest. Although various synthesis processes are known from the patent literature, there has never been a process by which o-substitution products can be obtained highly selectively from phenols having free o-positions with production times that are long enough for practical application.
Although phenol can be reacted to form 2,6-dimethyl phenol with a selectivity of the order of 99% in accordance with German Offenlegungsschrift No. 21 27 083, a selectivity of only 95% is obtained where o-cresol is used as the starting material.
German Offenlegungsschrift No. 19 48 607 describes a process in which o-cresol is converted into 2,6-dimethyl phenol with a selectivity of around 84%. Conversely, a selectivity of 98% is obtained with o-cresol as the starting product according to German Offenlegungsschrift No. 24 28 056. Where phenol is used, however, a selectivity of only 96,5% is achieved, falling to 92% after 150 hours.